1. Field of the Invention
The present invention relates to sun protection compositions for application to the skin, comprising special polyurethanes and special sun filter combinations, and also to the use of said polyurethanes and sun filter combinations for the preparation of sun protection products.
2. Description of Related Art
For years, tanned skin has been a synonym for attractive, healthy, sporty and successful people. In order to achieve this, people expose their skin to solar radiation. However, the solar rays have a harmful effect on the skin since they penetrate into the skin to varying depths depending on their wavelength. The shorter-wave radiation in the UVB region (wavelength: 280-320 nm) reaches the uppermost skin layer. Rays in the UVB region cause sunburn and are responsible for an increased risk of skin cancer. The longer-wave UVA rays (wavelength: 320-400 nm) penetrate into deeper skin layers. They lead to damage of the collagen and elastin fibres which are of essential importance for the structure and the strength of the skin. This leads, moreover, to premature skin ageing (formation of lines and wrinkles, irregular relief of the skin etc.). To protect the skin against solar radiations, photoprotective filter substances have been developed (UVA and UVB filters, contained in the form of positive lists such as Annex 7 of the Cosmetics Ordinance), which are used in cosmetic and dermatological compositions.
The sun protection products are often used on holiday or in leisure time on the beach or during sporting activities outside, where the body is in contact with water or perspiration. There is therefore the need to develop water-resistant and/or perspiration-resistant sun protection compositions. The production of such products is made possible through the use of selected technologies, such as, for example, water-in-oil (W/O) emulsions or through the use of hydrophobic film formers, such as, for example, alkylated polyvinylpyrrolidones.
The use of polyurethanes in sun protection compositions has already been described in the prior art. DE-A 10223693 describes the use of a polyurethanes which are formed from the polyaddition of 3-isocyanatomethyl 3,5,5-trimethylcyclohexyl-1-isocyanate and polyhydric alcohols, glycerides, hydroxy esters, silicone derivatives and/or amines. EP-A 1214929 describes the use of a film-forming, water-soluble or water-dispersible polyurethane for improving the water-resistance of a cosmetic or dermatological preparation comprising at least one UV filter. US-A 2003044364 describes the use of polyurethanes for improving the water resistance of sun protection formulations. EP-A 2 105 124 describes the use of special polyurethanes for improving application and also the skin feel when using the sun protection formulations.
However, there is furthermore the problem that prior art sun protection products, particularly in the case of a high sun protection factor (SPF), are difficult to spread on account of the often high required content of sun protection filter substances and, following application, leave behind an unpleasant waxy, sticky skin feel. Moreover, the content of certain sun protection filter substances is often restricted through legal provisions, meaning that in this regard limits are set in the selection of the composition to achieving a high SPF.